Loud-speaker diaphragm with transversely arched stiffener means



June 9, 1953 s. E. LEVY ET AL 2,641,329

LOUD-SPEAKER DIAPHRAGM WITH TRANSVERSELY ARCHED STIFFENER MEANS Filed May 29, 1950 5 Sheets-Sheet 1 INVENTORS Sidney llLeqy Ablwfi/imfl. 601mm ATTORNEY5 June 9, 1953 s. E. LEVY ETAL 2,641,329

LOUD-SPEAKER DIAPHRAGM WITH TRANSVERSELY ARCHED STIFFENER MEANS Filed May 29, 1950 5 Sheets-Sheen- 2 g ATTORNEYS.

June 9, 1953 s, E, L Y ET AL 2,641,329

LOUD-SPEAKER DIAPHRAGM WITH TRANSVERSELY ARCI-IED STIFFENER MEANS Filed May 29, 1950 5 Sheets-Shee 3 IN VENTORS ATTORNEYS.

Patented June 9, 1953' LOUD-SPEAKER DIAPHRAGM WITH TRANS- VERSELY ARCHED STIFFEN'ER MEANS Sidney E. Levy, White Plains, and Abraham B. Cohen, Bronx, N. Y., assignnrs to University Loudspeakers, Inc., White Plains, N. Y., a cor- ,poration of New York Application May 29, 1950, Serial No. 164,892

Claims.

The present invention relates to loud speakers, and more particularly, to diaphragms and stiffener means for diaphragms of loud speakers.

It has been found from experience with most 2 cone speaker diaphragm is reinforced or stiffened in the area adjacent to its apex, -accor-d ing to one form of the present invention, the voice coil no longer is subject to misalignment loud speakers that the diaphragms thereof are 5 or displacement with respect to the air gap by susceptible to deflection or mechanical distortion reason of stress or distortions in the loudspeaker when the supporting housing, basket or chassis chassis. is placed under stress, as'when mounted on an A further object of the invention is to in- ;irregular surface or 'bafile. This results in uncrease the rigidity of the speaker diaphragm due displacement of the position of the voice coil near its apex in order to prevent undue mechanin the usual air gap, causing rubbing .of the "ical displacement or misalignment of the voice voice coil against the pole pieces or other adcoil, while at the same time aiding or improvja'cent parts of the speaker, with consequent iingthe acoustical response of the diaphragm. distortion of the sounds or acoustical response Another object of the invention is to provide produced by the diaphragm. means for directing certain portions of the In acoustics, a :small opening in a baffle which acoustic spectrum such as the higher frequencies is inserted in a sound field acts itself as a point generated by the loud speaker, to areas Where source of sound. This is generally known as they will be rendered most desirable and subject the Huygens principle, wherein a pin-point to higher fidelity. perforation in a barrier which is placed in the Other and further objects and advantages of path of a plane wave becomes a separate radiator the invention will be hereinafter described, and byitself. Then as a separate radiator, it radiates the novel features thereof defined in the apa spherical wave. Therefore, a plane front wave pended claims. hitting a barrier in which there are small .aper- In the drawingstures, becomes transformed into many pinpoint Figure l is a view partly in section and partly spherical wave fronts. These will combine into in elevation, of a loud speaker unit of the eleca single spherical wave front provided that the tro-dynamic type, said loud speaker unit being perforated plate is curved. That is, when these provided with an improved diaphragm conperforations are placed on a spherical surface, structed in accordance with one embodiment curved wave is emanated which conforms 'to of the present invention: the envelope of the wavelets conforming to the Figure 2 is a sectional view through the dipinpoint sources. As is Well known in the art, aphragm of Figure l, as taken on the line 2-4 a curved wave front is a wave which radiates of Figure 1, looking in the direction of the over a wide angle and is therefore considerably arrows; diffused. If a second perforated plate is dis- Figure 3 ha fragmentary sectional view showposed in front of the first with the holes ofiing a modified form of the loud speaker diset, this primary curved wave will be doubly aphragm according to another embodiment of curved by hitting another set of perforations, th invention; the effect being compounded and a more Figure 4 is a sectional view taken on the line tremely diffused radiation results. Likewise, by 44 of Figure 3, looking in the direction of the perforating a member which .has a concave shape, arrows;

concentration or focusing effect will result. Figure 5 is a fragmentary se ti n i gen- Accordi y it is the P y P rpose of the erally similar to Figure 3, but showing still anpresent invention to provide means for improvother modified form of speaker diaphragm, acing the rigidity of diap the p p cording to another embodiment of the invention; 1- other type, as used in conventional loud Figure 6 is a sectional View taken on the line speakers, by the provision of one or more 6--'6 of Figure 5, looking in the direction of the stiffening elements, which elements serve at the arrows; same time as a form of zone plate or acoustic Figure "I is a fragmentary sectional view of duct to create dispersion or concentration, as still another modified form of diaphragm acdesired, of the high frequency energy generated cording to another embodiment of the invenby the center areas of the diaphragm and by tion; those areas of the diaphragm behind the Figure 8 is a sectional view taken on the line tiffener, 8-8 of Figure 7, looking in the direction of the We have found that when the surface of a arrows; and

Figure 9 is a, fragmentary sectional view generally similar to Figure 7, showing still another modified form of diaphragm according to a further embodiment of the invention.

Like reference characters designate corresponding parts in the several figures of the drawings, wherein Figure 1 illustrates a typical loud speaker of the moving coil type and to which the diaphragm of the present invention is applicable. It is to be understood, however, that the details of the speaker assembly are not material to the present invention, and are to be considered merely as one illustrative arrangement without limitation of the invention to this specific assembly.

According to the construction in Figure 1, the speaker assembly includes a pot provided at its center with a core H, both of magnetizable material such as soft iron or steel. Surrounding core II and disposed inside the pot I0 is a magnetizing coil I2. Pot I0 is adapted to be closed by a cover plate [3 whose inner edge portion cooperates with a portion [6 of the core to form pole-pieces between which is defined an annular air gap [8. Cover plate l3 and pot ID are of magnetizable material such as soft iron or steel so that upon energization of magnetizing coil [2, an intense magnetic field will be created within the air gap l8.

Disposed within the air gap I8 is a bobbin IQ of any suitable material, such as fiber, upon which is disposed a voice coil having suitable leads (not shown) for connection to a source of voice currents. The free end of the bobbin I9 is preferably closed by a generally conical or domeshaped cap 22 which may be formed of light, thin metal such as aluminum or copper, or it may be formed of thin fiber. The voice coil and bobbin are so proportioned as to move together axially within the air gap la in the manner customary with such types of loud speakers.

Attached to the bobbin [9 at the forward end thereof is a generally conical diaphragm 25 of any suitable material, such as stiff paper, metal, phenolic impregnated cloth or any other material. This diaphragm may have the outer edge or end thereof provided with flexing corrugations 26, if desired. A spider or suspension member 55 is mounted between the bobbin 1! and the cover plate 13. The extreme outer end or rim 2! of the diaphragm 25 is rigidly secured to the annular flanged mounting portion 28 of a diaphragm supporting housing, basket or chassis 29, as by a suitable ring 29a. Housing 29 is provided at its inner end with a mounting flange 30 suitably apertured to accommodate bolts or screws 3| to maintain pot l0, front plate I3 and housing 29 rigidly assembled in predetermined position. The entire speaker may be mounted by bolting annular flanged portion 28 to any suitable baffle (not shown) in a manner well known in the art.

Mounted near the apex of diaphragm 25 are stiffening members 32 and 33. The stiffening members are so spaced as to provide chambers 34 and 35. Staggered perforations 36 are provided in the stiffening members 32 and 33 so as to bend and direct the frequencies generated in the chambers 34 and 35, as well as those frequencies emanating from the dome cap 22, thereby affording directional control of the acoustical frequencies.

In Figure 3, the construction of the stiffening members 31 and 38 is similar to that of Figure 1, except that the perforations are provided with tube-like extensions 39 projecting outwardly of 4 the diaphragm 26 to direct the high frequency sound waves over a given area in a diverging manner.

Another modification is illustrated in Figure 5, wherein the extensions 42 on the stiffening members and 4| are so inclined as to direct the sound waves in a converging manner, the focal point depending upon the radius of members 40 and 4|.

One or more of the stiffening members shown in Figures 1, 3 and 5 may be used, depending on the size and flexibility of the diaphragm 25. Generally, the smaller diaphragms require but one stiffening member, while the larger diaphragms require two or more of the stiffening members to prevent undue displacement of the voice coil bobbin, and the voice coil carried thereby.

In Figure 7, another modification is illustrated, wherein the stiffening member 45 is horn-like in form and is attached to the apex of the diaphragm 25 between the dome cap 22 and the marginal edge of the diaphragm which surrounds the same. This region is indicated by the reference character 43. The opposite end of the horn-like member 45 is secured to the side of the diaphragm 25 at 44, and located a predetermined distance from the apex to provide sufficient rigidity for the diaphragm according to the type and size used. Sound waves generated in chamber are directed outwardly through passages 41.

Still another modified arrangement is illustrated in Figure 9, wherein the horn-like member 46 is similar to that of Figure '7 except that the smaller end of the horn is secured to the face of the dome cap 22 at the point 49 which is relatively nearer to the central axis of the dome cap. The sound waves generated in chamber 5! are directed outwardly through passages 48.

From the foregoing description, it will be apparent to those skilled in the art that we have provided a novel arrangement and construction of loud speaker diaphragms for preventing undue displacement of the voice coil, and eliminating much of the sound distortion which otherwise would be created under certain conditions. By employing diaphragms constructed in accordance with the present invention, a much wider distribution and higher fidelity is attained in the higher frequencies that normally travel in a more-or-less straight line, and which, in many instances, cannot be detected in zones spaced from the center of the speaker.

While the specific details have been herein shown and described, the invention is not confined thereto as changes and alterations may be made without departing from the spirit thereof as defined by the appended claims.

We claim:

1. An acoustic diaphragm for loud speakers, comprising an acoustical energy-responsive diaphragm member of substantially conical form having a relatively rigid transversely arched stiffener member secured at its outer marginal edge to an intermediate portion of the diaphragm member and extending across the latter, said stiffener member having a plurality of relatively small sound-radiating perforations therethrough, the perforations of said stiffener member being spaced from each other and each perforation having its axis inclined at an angle to the central axis of the diaphragm member,. and the perforated stiffener member having the property of directional control of high frequency propagation generated from the center of the diaphragm member.

2. An acoustic diaphragm as defined in claim 1, wherein the stiffener member has the form of a transversely arched perforated plate bridging the central area of the diaphragm member.

3. An acoustic diaphragm as definedin claim 1, wherein the stiifener member has the form of a horn-shaped member secured at its smaller end to said diaphragm and secured at its larger end to said diaphragm at a substantial distance from the smaller end foresaid.

4. An acoustic diaphragm for loud speakers, comprising an acoustical energy-responsive cone member having a relatively rigid transversely arched horn-shaped stiffener member disposed within the same and secured at its outer marginal edge thereto within the region adjacent to the apex thereof and extending across 'said cone member, said stiffener member having, a plu rality of relatively small sound-radiating per- Iorations therethrough, each having its axis inclined at an angle to the central axis of said cone member, the apex of said cone member having an imperforate closure member mounted thereon and extended transversely thereacross, said perforated stiffener member having its inner margin secured to said closure member, and said perforated stiffener member having the property of directional control of high frequency propagation generated from the center of said cone member.

5. An acoustic diaphragm for loud speakers, comprising an acoustical energy-responsive cone member, a plurality of axially spaced relatively rigid barriers disposed in the path of the sound wave front generated by said cone member, each of said barriers having a plurality of relatively small sound-radiating perforations therethrough, the perforations of the respective barriers each having its axis inclined at an angle to the central axis of said: cone member and being laterally ofiset relative to each other, and each of said barriers being supported solely by said cone member on at least one annular contacting surface in the zone of the apex of said cone member and vibratable therewith, while having the property of directional control of high frequency propagation generated from the center of the cone member.

SIDNEY E. LEVY.

ABRAHAM B. COHEN.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,673,939 Farrand June 19, 1928 1,757,719 Kent May 6, 1930 1,846,937 Bedford Feb. 23, 1932 1,876,306 Laing Sept. 6, 1932 2,007,747 Ringel July 9, 1935 2,070,977 Quinnell Feb. 16, 1937 2,124,834 Stenger July 26, 1938 2,141,423 Tolerton Dec. 27, 1938 2,193,399 Fisher Mar. 12, 1940 2,231,479 Perry Feb. 11, 1941 2,269,284 Olson Jan. 6, 1942 2,580,439 Kock Jan. 1, 1952 FOREIGN PATENTS Number Country Date 368,344 Great Britain Mar. 4, 1932 611,056 Great Britain Oct. 25, 1948 

